Hall effect signalling gauge

ABSTRACT

A signalling gauge may utilize a non-captivating, magnetically actuated switch element which is mounted in an influence zone of a path of a magnet carried by an indicating pointer of the gauge. The gauge may operate despite the presence of dust, dirt or other pollutants for an extended period of time without inducing sparks or arcing often associated with electromechanical contacts. Hall effect switch elements such as latches or digital switches may be utilized as a switch element for signalling to drive an audio or visual alarm or a digital signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a signalling gauge and more particularly to amagnetically- activated signalling gauge where the visual indication ofthe reading is not affected by a magnetic field of an actuating magnet.

2. Description of the Related Technology

Signalling gauges are instruments or meters which are utilized tomonitor various parameters such as temperature, pressure, liquid levelsor various electric properties. These instruments are specificallyconfigured to give an indication when the monitor condition reaches somepredetermined point.

In prior signalling gauges, the predetermined point is typicallydetected by electromechanical contacts. One contact is located on thereading pointer of the meter. A second contact may be either fixed oradjustable and located in the travel path of the pointer contact. U.S.Pat. Nos. 3,586,799 and 4,021,627, the disclosures of which areexpressly incorporated herein, show electromechanical contact signallinggauges. (Furthermore, various gauges of this type have been sold underthe registered trademark SWICHGAGES by Frank W. Murphy MFR., Inc.)

Electromechanical signalling gauges are quite adequate for a greatnumber of purposes. They do, however, possess a number of shortcomings.The most significant shortcoming is the electrical contact integrity.The lifespan of electromechanical contacts is finite and depends on thenumber of operations in the environment to which they are exposed.Exposure to atmospheric conditions containing dirt, dust or variouschemical gases can significantly degrade contact integrity andnegatively impact on contact life span. As a result, frequent contactcleaning and/or replacement is necessitated.

A further drawback is the effect the mechanical contact has on themovement integrity. In order to establish or break electrical contact, aforce significant to the operation and accuracy of the meter must oftenbe applied to the indicating pointer. This precludes or significantlycomplicates the utilization of sensitive or balanced meter movements insignalling gauge applications. Electromechanical contacts are quitebulky and do not lend themselves to installation on aircoil orD'Arsonval movements such as those found in automotive instruments ormany electrical condition monitoring instruments.

Another significant disadvantage of electromechanical contacts is thepossibility of spark production. According to the American PetroleumInstitute, Class I Division II environments classified as hazardous maynot contain electrical contacts which are capable of producing a spark.Such a contact may result in ignition of flammable gases which may bepresent. Standard electric or electromechanical contact signallinggauges must be isolated from this environment by either large, expensiveexplosion proof enclosures or electronic barriers.

A final disadvantage of conventional electromechanical contacts is theinability to efficiently switch low level digital milliamp levels.Recommended operating levels for electromechanical contacts aresignificantly higher than conventional digital switching signal levels.

Other signalling gauges have utilized opto electronic sensors. This hasnot proved satisfactory in many applications because such gauges requirehermetic sealing in order to operate for any period of time. Dust anddirt buildup significantly impairs the sensor, thereby rendering thegauge inoperative. The sealing provisions required add a significantexpense to the production of the instruments.

SUMMARY OF THE INVENTION

It is an object of the invention to enhance the operationalcharacteristics of signalling gauges in view of the operationallimitations inherent in the utilization of electromechanical and opticalsensing contacts in a signalling gauge. The signalling gauge, accordingto the invention, is a unique, versatile device which may accuratelyoperate over long periods of time in remote locations or hostileenvironments.

The signalling gauge is made up of a gauge movement which is arrangedand connected to respond to a particular sensed condition. The sensedcondition may be a pressure, temperature, level or electricalcharacteristic. Examples of various movements which may be utilized areBourdon tube type movements or D'Arsonval type movements. The movementis connected to a reading pointer which typically passes over a gaugeface plate to provide a visual reading of the sensed condition. Anoncaptivating, magnetically actuated switch element is arranged tocooperate with a magnet, typically mounted on the indicating pointer inorder to signal a predetermined reading of the meter movement. The orderto avoid influencing the meter reading or damaging the meter movement.The mechanical resistance of electromechanical contacts influences theindicating needle and, therefore, affects the reading and the output ofthe meter. Utilization of an electromagnetic/mechanical switchingelement such as a reed switch also results in some mechanical influenceon the indicating pointer or meter movement. Any such influence is to beavoided in order to prolong the lifespan of the meter and maintainreading integrity.

An example of a noncaptivating, magnetically actuated switch element isa Hall effect switching device such as, for example, a Hall effecttransistor, digital switch, or latch. The term "noncaptivating" isintended to preclude elements where the eletromagnetic interactionbetween a switch element and the actuating magnet results in a forcetending either to retard or induce relative motion between the switchingelement and the actuating magnet path.

The actuating magnet may be a very small, lightweight element such as aone gram magnet mounted on an indicating pointer. Various Hall effectelements may be utilized, such as a SPRAGUE UGS-3075U bipolar Halleffect digital latch or a UGS-3140U ultra-sensitive Hall effect switch,depending on desired circuit capabilities and properties.

The Hall effect switching device may be permanently mounted on a faceplate to provide a switch point. Advantageously, the switching elementmay be recessed, flush mounted, or mounted beneath a face platecovering. It is necessary that the magnetically actuated switchingelement is mounted proximate to the magnet path and falls within thezone of influence of the magnet. Alternatively, switching elements maybe mounted on variable pointers which may be adjusted according todesired operating parameters.

Typically, the signalling gauges are set up to operate in a slide bymode where a flux axis of the actuating magnet may be eitherperpendicular or parallel to a travel path of the magnet. A bipolarlatch and a magnet axially aligned with the travel path may beconfigured with a leading activating pole of the magnet on an increasingreading or with a trailing activating pole, depending on the applicationand switching requirements.

According to a preferred embodiment, a control circuit may be connectedto one or more signalling gauges. The control circuit may control one ormore functions depending on the operating parameters sensed by thesignalling gauges. The control circuit may be a simple control circuitor a programmable logic controller.

The switching element may be connected to an indicator. The indicatormay be provided to alert someone of the sensed condition. Suchindicators may include visual or optical devices such as a lamp bulb orLED. The indicator may be an audio alarm such as a bell or a buzzer.

Typical applications of signalling gauges, according to the invention,include a variety of circuit applications. Signalling gauges, accordingto the invention, may be utilized to indicate or control an alarm upondetection of a predetermined condition such as a high or a low pressurecondition in a fluid system, a high temperature or low fuel levelcondition in a piece of heavy machinery, or an excessive current load inan electrical circuit. The signalling gauges may also be utilized aspart of a control circuit, for example, controlling a pump to maintainpressure within a predetermined range or as a monitor/alarm for apipeline cathodic protection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a signalling gauge according to theinvention.

FIG. 2 shows a front view of the embodiment according to figure one.

FIG. 3 shows an alternative embodiment with an adjustable contact arm.

FIG. 4 shows a plan view of a signalling gauge according to theconfiguration of FIG. 3.

FIG. 5 shows a plan view of an alternative embodiment according to FIG.3.

FIG. 6 shows a wiring diagram for an embodiment of a signalling gaugeaccording to the invention.

FIG. 7 shows a multi contact signalling gauge.

FIG. 8 shows a schematic circuit diagram for an alternative embodimentof a signalling gauge according to FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 schematically illustrate an embodiment of a signallinggauge with a flush mounted Hall effect switching device 10 arranged on aface plate 11 of the signalling gauge. A meter movement 12 is providedwhich responds to a sensed condition 13. The sensed condition 13 may bepressure in the case of a Bourdon tube movement or an electricalpotential in the case of a D'Arsonval movement. The movement 12translates the magnitude of the sensed condition into rotational motionof a shaft 14 connected to an indicating pointer 15. A magnet 16 ismounted on the indicating pointer in such a fashion that its pathcarries it close enough to the Hall effect switching device 10 toinfluence switching of the element 10.

FIG. 3 shows an embodiment with a Hall effect switching unit 30 mountedon an adjustable arm 31. The adjustable arm 31 is connected to anadjusting knob 32 which extends through a clear lens 33. The adjustablearm 31 may be pivoted in order to set the switching point of thesignalling gauge. A magnet 34 is connected to a pointer 35. The pointer35 is rotated by motion of the shaft or stand 36 controlled by the gaugemovement. (Not shown). Alternatively, the pointer may be rotated by acrankarm and pivoted on a shaft in embodiments with a fixed shaft.

FIGS. 4 and 5 show two applications for the configuration illustrated inFIG. 3. Gauge 40 is adapted to monitor pressure while gauge 50 isadapted to monitor temperature. Each instrument contains a face plate41, 51 which displays a graduated dial visible through a clear lens.Knobs 42, 52 are located on the front of the gauge and adapted tocontrol the "contact" arms 43, 53. Each arm carries a Hall effectswitching element 44, 54. An extension of the arm is provided as avisual indication of the location of the switch point. An indicatingpointer 45, 55 is arranged to display the sensed reading of the gauge.The indicating pointers carry an activating magnet (not shown in theview of FIGS. 4 and 5) positioned to actuate or deactuate the Halleffect switching device on passage thereover. Each gauge may carry anLED signalling indicator 46, 56, as a visual indication that thepredetermined set point has been attained. (optional)

FIG. 6 shows an electrical schematic of a signalling circuit accordingto an embodiment of the invention. A bipolar Hall effect digital latch61 is utilized as the non captivating magnetically actuated switchelement. The Hall effect element may be a UGS-3075 manufactured bySprague. The Hall effect element is connected through a voltage divider62 to a switching transistor 63. The switching transistor may beconnected to a signalling LED 64 through a resistor 65. Additionally,the switching transistor may be connected to control inputs of aflashing light element 66 and/or an electronic chime 67. In operationthe indicating pointer, illustrated schematically at 68, sweeps themagnet 69 past the Hall effect element 61.

FIGS. 7 and 8 show a multiple contact signalling gauge. The signallinggauge is configured as a pressure meter 70. A pressure input port 71 islocated on the pressure meter. Adjustable contact pointers 72 and 73 areconnected to knobs 74 and 75 respectively. Adjustable pointer 73 carriesa low set point Hall effect switch 76 and adjustable pointer 72 carriesa high set point Hall effect switch 77. Switch elements 76 and 77 mayadvantageously be ultra-sensitive Hall effect switches such as SPRAGUE,UGS 3140 switches. The switch elements 76 and 77 are shown on theexterior sides of adjustable pointers 73 and 72 for illustrativepurposes only. The switching elements in practice are located on anopposing side of the pointers, facing the meter indicating pointer 78which bears a magnet 79. The low set point switch element 76 isconnected to a low set point switch "on" LED 80. The high set pointswitch 77 is connected to a high set point switch "on" LED 81. Accordingto an advantageous embodiment, this setup may be utilized in order tomaintain pressure in a monitored tank between amounts called foraccording to the adjustable pointers. The meter may, for example, beconnected to an auxiliary control circuit 82 which in turn controls apump (not shown) through a series of switched contacts 83. The auxiliarycontrol circuit 82 may be connected by a lead 84 and located remotely.The auxiliary control circuit may include a voltage regulator 85. TheHall effect switch elements may be connected via "set" (S) and "reset"(R) inputs to a flip flop or latch circuit 86 which in turn controls arelay 87.

The illustrated embodiments are shown by way of example. The spirit andscope of the invention is not to be restricted by the preferredembodiment shown.

I claim:
 1. A signalling gauge comprising:a gauge movement responsive to a sensed condition; a pointer mounted on said gauge movement; a magnet attached to said pointer; a noncaptivating, magnetically actuated switch element mounted in an influence zone of the path of said magnet.
 2. A gauge according to claim 1 wherein said switch element is a Hall effect device.
 3. A gauge according to claim 2 wherein said Hall effect device is mounted on a gauge face plate.
 4. A gauge according to claim 3 wherein said Hall effect device is recessed into said face plate.
 5. A gauge according to claim 3 wherein said Hall effect device is a bipolar Hall effect digital latch.
 6. A gauge according to claim 5 wherein said magnet axis is aligned in said path and perpendicular to a sensing axis of said Hall effect digital latch.
 7. A gauge according to claim 6 wherein a rising reading leading end of said magnet exhibits a flux polarity corresponding to an activating flux polarity of said Hall effect digital latch.
 8. A gauge according to claim 5 further comprising: a control circuit responsive to said Hall effect digital latch.
 9. A gauge according to claim 8 wherein said control circuit comprises at least a programmable logic controller.
 10. A gauge according to claim 2 further comprising an indicator responsive to said Hall effect device.
 11. A gauge according to claim 1 wherein said indicator is an optical indicator.
 12. A gauge according to claim 1 wherein said indicator is an audio indicator.
 13. A gauge according to claim 2 wherein said movement is a Bourdon tube type of movement.
 14. A gauge according to claim 2 wherein said movement is an electrical movement.
 15. A gauge according to claim 14 wherein said movement is a D'Arsonval type movement.
 16. A gauge according to claim 2 wherein said Hall effect device is mounted on an adjustable member.
 17. A gauge according to claim 16 further comprising a plurality of Hall effect devices mounted on adjustable members.
 18. A gauge according to claim 17 wherein said Hall effect devices are switches; and further comprising at least: a latch connected to at least two of said switches.
 19. A gauge according to claim 17 further comprising a control device connected to said Hall effect devices. 